1. Field of the Invention
This invention relates to the general field of electrical connectors and is particularly concerned with a submersible, set-screw type, electrical connector.
2. Background of the Invention
Electrical distribution systems are used extensively in most industrialized countries. These distribution systems typically include power cables, transformers and connectors for linking the components together. Some distribution systems have cables suspended from poles anchored into the ground so that the cables are located substantially above the ground surface. In such instances, the transformers and connectors are also mounted on the poles above the ground.
Newer electrical distribution today is underground. This includes not only the conductor but the transformer and the set screw connector. The connections are usually made below grade in a hand hole, manhole, vault or fairly deep hole with confined space. Many such connections are made in mud or muddy water. If the connection is not below water initially, over its service life, it will be due to rains or floods or even normal seasonal fluctuations of ground water.
To provide such connectors with a longer service life, submersible connectors have been developed. Such connectors are provided with a molded waterproof encasement. Problems, however, arise both where the conductors enter the case and more particularly where access to the set screw is required.
Many such connectors include long projecting sleeves at the conductor ports which are plugged with elongated grommets known as “rockets.” The rockets include stepped tips which are cut off at a selected step depending on the size of the conductor. The conductor is inserted through the cut-off tip of the rocket which now becomes an elongated sleeve grommet. Both are inserted into the long sleeve of the case with the grommet sealing against the interior of the sleeve and the projecting tip of the conductor extending beneath the path of the set screw. The preparation and insertion of the conductor is typically a two-handed operation for a technician.
Access to the set screw is through a port provided by a somewhat shorter cylindrical sleeve projection. The port is provided with a removable cap or plug which is supposed to provide a watertight connection. When the plug is removed, access is provided to the recessed hex head set screw.
The submersible connection in each of the paired sleeve ports includes the rocket and the watertight plug. When the connection is initially installed, only some of the paired ports may be used and additional connections may be made later, if ever.
When a connection is made, the rocket is removed, cut to size and inserted on the end of the conductor. Before inserting the conductor, the technician has to remove the plug on the corresponding set screw port sleeve projection and make sure the set screw is backed out. This is done by inserting a hex driver such as an Allen wrench and backing out the set screw. Only then is the conductor inserted to a position to be clamped by the set screw. Because of the tight connection of the plug in its sleeve, such plugs usually have to be removed with a pair of pliers. The set screw is then tightened with the hex driver to complete the electrical connection. While the modified rocket seals the conductor port, the plug has to be replaced and properly seated to maintain the waterproof integrity of the case. The technician must perform all of these operations usually with heavy gloves on, and in a cramped dark, and wet space. It is not uncommon for the bottom of the space to be filled with muddy water.
Since the technician often wears gloves, manual dexterity is compromised and the plug or rocket is often dropped. Commonly, after the connection is made, the technician must grope in the mud or water to retrieve the plug or rocket.
If the plug can not be found readily, the common practice is to cover the port hole with a strip or strips of electrical tape, for a makeshift seal, if a seal at all. One major cause of failure of this type of connector is the loss of watertight rockets and plugs. The absence of a proper plug and a properly sized rocket allows water to penetrate the connector.
Unfortunately, water ingress, particularly where the plug and rocket is intended to seal against the jacket of the conductor end, may result in corrosion and failure of the connector. When properly installed, such plugs and rockets do not permit water ingress. Unfortunately, if improperly installed the seal provided by the plug and rocket may not be sufficient to keep water out. Accordingly, water enters and degrades the electrical connection resulting in premature failure of the connector. The inability to easily inspect the connectors in underground hand holes or vaults is also problematic, especially in light of the opportunity for errors in making the connections.
Less highly skilled technicians are more commonly used to install the connectors as a cost savings measure for utilities and their subcontractors. Instances of improper installation are more likely to occur as training and skill levels are reduced, and while at the same time greater production rates are required. For example, an improperly trained technician may cut the rocket at a ring that is too large to correctly seal on the conductor. Of course, the larger the ring, the less insertion force required to position the conductor through the rocket. Weeks, months or years after installation, water penetrates the area of the “seal” and causes connector failure.
Therefore, a submersible electrical set screw connector which could more easily be used and properly installed with less chance for human error in the cramped and wet environment of an underground connection is needed. The ability to easily and readily inspect the connection is also highly desired. Moreover, such a connector where components such as the rockets or plugs would not get lost and would remain handy to the technician to properly and efficiently complete a long lasting failure free set screw connection is also desired.
Another problem associated with known electrical connectors of this type stems from the use of conductors having a number of strands encased in a plastic sheath. Whether the conductors are manufactured as segmented or non-segmented center conductors from aluminum wire strands or copper wire strands, the end portion of the sheath must be removed from the conductor to expose the wire strands for electrical connection. The technician then inserts the unsheathed tip end of the conductor into the aperture in the set screw connector. In many instances, numerous strands of the conductor splay outwardly from the remaining strands as the unsheathed end of the conductor is inserted through various holes, ports or apertures in such submersible and allegedly water-tight connection systems. Such frayed conductors with splayed strands are much more difficult for the technician to efficiently and cleanly insert into the connector to accomplish a proper connection.
Moreover, proper installation of the conductors should avoid splaying the conductor strands. Additionally, the design should allow for a variety of sizes of conductors and tap lines to be accommodated with a minimum of installation effort and without specialized tools. The connector must be designed so that taps can be made by tap lines and conductors added and withdrawn after the original installation.
Another problem associated with known electrical connectors of this type is ensuring a proper seal is created between the electrical connector and the enclosure, as any leakage in the wet environment leads to oxidation of connections and device failure. A less highly-trained technician working on the electrical connector in darkness is especially susceptible to making mistakes when closing these devices, such as allowing contaminants to get into the seal surface. Leaving the enclosure too loosely or too tightly connected to the electrical connector also frequently leads to failure of the seal. Therefore, it would be desirable to add features to an electrical connector to minimize technician error which contributes to seal and electrical connector failure.